Network interface device

ABSTRACT

A network interface device includes a passive path between an entry port and a first port. The network interface device also includes an active path between the entry port and a second port. The network interface device also includes a buffer in the active path configured to absorb, attenuate, terminate, or isolate radio-frequency (RF) signals. The network interface device also includes a switching element in the active path configured to cause the RF signals to bypass the buffer when the network interface is in a first state that exists during powered operation of the network interface device, and direct the RF signals to the buffer when the network interface device is in a second state that exists during non-powered operation or faulted operation of the network interface device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/154,804, filed on Oct. 9, 2018, which claims priority to U.S.Provisional Patent Application No. 62/569,130, filed on Oct. 6, 2017.The entirety of both applications is incorporated by reference herein.

FIELD

The present disclosure is directed to cable television (CATV) networkcommunication devices. More particularly, the present disclosure relatesto an entry adapter for a CATV network.

BACKGROUND

CATV networks supply and distribute high frequency “downstream” signalsfrom a main signal distribution facility, known as a “headend,” topremises (e.g., homes and offices) of subscribers of the CATV networks.The downstream signals can be provided to subscriber equipment, such astelevisions, telephones, and computers. In addition, most CATV networksalso receive “upstream” signals from subscriber equipment back to theheadend of the CATV network. For example, a set top box can use anupstream signal to send information for selecting programs for viewingon a television. Also, upstream and downstream signals can be used bypersonal computers connected through the CATV infrastructure to theInternet. Further, voice over Internet protocol (VOIP) telephones canuse upstream and downstream signals to communicate telephoneconversations.

To permit simultaneous communication of upstream and downstream signals,and to permit interoperability of the subscriber equipment and theequipment associated with the CATV network infrastructure, thedownstream and upstream signals are confined to two different frequencybands. For example, in CATV networks, the downstream frequency band canbe within the range of about 54 to 1002 megahertz (MHz) and the upstreamfrequency band can be within the range of about 5 to 42 MHz.

Downstream signals can be delivered from the infrastructure of the CATVnetwork to the subscriber premises via a network interface device(a.k.a., an entry device, an entry adapter, a terminal adapter, or adrop amplifier). A network interface device can be a multi-port device,in which an upstream entry port connects to a drop cable from theinfrastructure of the CATV network, and one or more input/output ports(hereinafter “ports”) connect to subscriber equipment distributed arounda premises of a subscriber.

The network interface device can include two paths: an active RF signalcommunication path (i.e., “active path”) and a passive RF signalcommunication path (i.e., passive path”). The active path can includeactive components (e.g., powered devices) that amplify and/or conditiondownstream signals received from the CATV infrastructure and conductthem to one or more ports of the CATV entry adapter. Subscriberequipment connected to these active ports benefits from thisamplification of the CATV downstream signal. However, loss of power tothe entry adapter prevents communication of active CATV signals by theactive components. In comparison, the passive path lacks any activecomponents. As such, subscriber equipment connected to these passivepath can operate in the event of power loss. For example, the passivepath may be used to provide a “lifeline telephone service” that remainsoperative when a subscriber premises losses power.

SUMMARY

A network interface device is disclosed. The network interface deviceincludes an entry port configured to connect the network interfacedevice to a radio-frequency (RF) signal source. The network interfacedevice also includes a splitter/combiner configured to split adownstream RF signal received by the entry port from the RF signalsource into a first portion of the downstream RF signal and a secondportion of the downstream RF signal. The network interface device alsoincludes a passive port configured to connect the network interfacedevice to a first client device. The network interface device alsoincludes an active port configured to connect the network interfacedevice to a second client device. The network interface device alsoincludes a passive RF signal path coupling the entry port to the passiveport. The network interface device also includes an active RF signalpath coupling the entry port to the active port. The network interfacedevice also includes an amplifier circuit configured to amplify thesecond portion of the downstream RF signal in the active RF signal path.The active port is configured to provide an upstream RF signal throughthe amplifier circuit to the entry port.

In another embodiment, the network interface device includes an entryport configured to receive a downstream radio-frequency (RF) signal froma signal source. The network interface device also includes a first portconfigured to receive a first portion of the downstream RF signal fromthe entry port via a passive path and configured to transmit a firstupstream RF signal to the entry port via the passive path. The networkinterface device also includes a second port configured to receive asecond portion of the downstream RF signal from the entry port via anactive path and configured to transmit a second upstream RF signal tothe entry port via the active path. The network interface device alsoincludes a decibel limiting device in the active path having a firststate and a second state. The decibel limiting device is configured toin the first state, pass the second portion of the downstream RF signaland the second upstream RF signal via the active path, and in the secondstate, absorb, attenuate, terminate, or isolate the second portion ofthe downstream RF signal, the second upstream RF signal, or both by atleast 10 decibels.

In another embodiment, the network interface device includes a passivepath between an entry port and a first port. The network interfacedevice also includes an active path between the entry port and a secondport. The network interface device also includes a buffer in the activepath configured to absorb, attenuate, terminate, or isolateradio-frequency (RF) signals. The network interface device also includesa switching element in the active path configured to cause the RFsignals to bypass the buffer when the network interface is in a firststate that exists during powered operation of the network interfacedevice, and direct the RF signals to the buffer when the networkinterface device is in a second state that exists during non-poweredoperation or faulted operation of the network interface device.

In another embodiment, the network interface device includes a firstport configured to allow a downstream radio-frequency (RF) signalreceived from a signal source to be communicated through the networkinterface device, and a second port configured to allow an upstream RFsignal to be communicated to the first port. The network interfacedevice also includes a decibel limiting device configured to switchbetween a first state, where the downstream RF signal and the upstreamRF signal are permitted to be communicated between the first and secondports, and a second state, where the downstream RF signal and theupstream RF signal are restricted from communicating between the firstand second ports by a predetermined decibel limit.

In yet another embodiment, the network interface device includes a firstport configured to allow a downstream signal received from a signalsource to be communicated through the network interface device, and asecond port configured to allow an upstream signal to be communicated tothe first port. The network interface device also includes a decibellimiting device configured to switch between a first state, where thedownstream signal and the upstream signal are permitted to becommunicated between the first and second ports, and a second state,where the downstream signal and the upstream signal are restricted fromcommunicating between the first and second ports by a predetermineddecibel limit.

Other and different statements and aspects of the invention appear inthe following claims. A more complete appreciation of the presentinvention, as well as the manner in which the present invention achievesthe above and other improvements, can be obtained by reference to thefollowing detailed description of a presently preferred embodiment takenin connection with the accompanying drawings, which are brieflysummarized below, and by reference to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of an example of an environment forimplementing systems, devices, and processes in accordance with aspectsof the present disclosure. In other embodiments, the network interfacedevice (NID) may be placed external to the premises.

FIG. 2A is a functional block diagram of an example of a networkinterface device in accordance with aspects of the present disclosure.

FIG. 2B is a functional block diagram of another example of a networkinterface device in accordance with aspects of the present disclosure.

FIG. 3A is a functional block diagram of an example of a resistivebuffer in accordance with aspects of the present disclosure.

FIG. 3B is a functional block diagram of another example of a resistivebuffer in accordance with aspects of the present disclosure.

FIG. 4 is a functional block diagram of an example of a matchedresistive buffer in accordance with aspects of the present disclosure.

FIG. 5 is a functional block diagram of an example of an absorptivelow-pass filter buffer in accordance with aspects of the presentdisclosure.

FIG. 6 is a functional block diagram of an example of an absorptivehigh-pass filter buffer in accordance with aspects of the presentdisclosure.

FIG. 7A is a functional block diagram of an example of a multi-outputnetwork interface device in accordance with aspects of the presentdisclosure.

FIG. 7B is a functional block diagram of another example of amulti-output network interface device in accordance with aspects of thepresent disclosure.

FIG. 8 is a functional block diagram of an example of a multi-outputnetwork interface device in accordance with aspects of the presentdisclosure.

FIG. 9A is a functional block diagram of an example of a buffer inaccordance with aspects of the present disclosure.

FIG. 9B is a functional block diagram of an example of a shunt buffer inaccordance with aspects of the present disclosure.

FIG. 9C is a functional block diagram of an example of a series bufferwith a simplified absorptive band-pass filter in accordance with aspectsof the present disclosure.

DETAILED DESCRIPTION

A network interface device in accordance with aspects of the presentdisclosure preserves signal quality in a passive path (e.g., a low-lossVOIP path) in the event of power loss or other fault that interruptspower supplied to an active path. In some implementations, the networkinterface device isolates the passive path to minimize interference(e.g., distorted and/or reflected signals) from the active path. Forexample, in response to power loss or other fault, the network interfacedevice can increase isolation of the active path from the passive pathby automatically placing a resistive attenuator or absorptive filterbetween the passive path and the active path.

FIG. 1 illustrates a block diagram of an example of an environment 3 forimplementing systems, devices, and processes in accordance with aspectsof the present disclosure. The environment 3 can include a source 5, anda premises 7. The source 5 can be a network of an information service,such as a CATV network. In some implementations, the premises 7 can be alocation of a client of the source 5, such as a subscriber of the CATVnetwork. For example, the premises 7 can be a residence, an office, abusiness, and the like. In accordance with aspects of the presentdisclosure, the premises 7 can include a network interface device 10communicatively connecting client devices 13 and 15 at the premises 7 tothe source 5. The client devices 13 and 15 can be, for example, CATVdevices, Internet devices, VoIP devices, and/or data communicationdevices installed in the premises 7. Optionally, the NID may beinstalled external to the premises while still establishing the sameinterconnectivity between the cable network and the premises equipment

In some implementations, the network interface device 10 includes anentry port 103, an optional power input port 105, optional remote powerconnectivity through a choke to active port 108, a passive port 107, andan active port 108 that make external connections for communicatingradio frequency (RF) signals 113-118 and power 109. The passive port 107and the active port 108 can be input/output ports electrically coupledto the client devices 13 and 15, and can communicate RF signals 115-118between the network interface device 10 and the client devices 13 and15. The entry port 103 can be an input/output port electrically coupled(directly or indirectly) to the source 5 (e.g., via a drop line from anetwork), and can receive downstream RF signals 113 from the source 5.The entry port 103 can also transmit upstream RF signals 118 from theclient devices 13 and 15 to the source 5. The power input port 105 canbe an input port that receives the power (PWR) 109 from an externalpower source (not shown) that powers components of the network interfacedevice 10. Alternatively, the remote power connected to the active port108 can be an input port that receives the power (PWR) 109 from anexternal power source (not shown) that powers components of the networkinterface device 10.

FIGS. 2A and 2B are functional block diagrams of an exemplary networkinterface device 10 in accordance with aspects of the presentdisclosure. The network interface device 10 can include a regulator 101and a fault detector 102. The network interface device 10 can alsoinclude an entry port 103, a power input port 105, a passive port 107,and an active port 108, which can be the same or similar to thosepreviously described herein. Additionally, the network interface device10 can include a splitter/combiner 110, an active path 111 (indicated bya first dashed line) and a passive path 112 (indicated by a seconddashed line).

The regulator 101 can be a power device that receives power 109 from thepower input port 105 and outputs a voltage V (e.g., 10 VDC, 9 VDC,and/or 5 VDC) for driving active devices, relays, transistors, and otherpowered devices of the network interface device 10. The fault detector102 can be a power device connected to an output of the regulator 101that selectively interrupts power output by the regulator 101 to thecomponents of the network interface device 10 under a fault condition.The fault condition can be, for example, a power surge, a powerfluctuation, or a power drop sensed by the fault detector 102.

The splitter/combiner 110 is a passive device having a common terminal(C) electrically coupled to the input port 103, a first leg (1)electrically coupled to the active path 111, and a second leg (2)electrically coupled to the passive path 112. For example, thesplitter/combiner 119 can be a one-in, two-out splitter device. In someimplementations, the splitter/combiner 110 provides high isolation(e.g., 25 decibels (dB)) between its legs (1, 2) to minimize leakage ofRF signals (e.g., upstream RF signals 116 and 117) between the activepath 111 and the passive path 112.

The splitter/combiner 110 can communicate bidirectional RF signals113-118 between the entry port 103 and the passive port 107, and betweenthe entry port 103 and the active port 108. In the downstream direction,the splitter/combiner 110 splits a downstream RF signal 113 receivedfrom a source (e.g., the source 5 shown in FIG. 1, such as a CATVheadend) into a downstream RF signal 114, which is communicated to theactive port 108 via the active path 111, and into a downstream RF signal115, which is communicated to the passive port 107 via the passive path112. In the upstream direction, the splitter/combiner 110 combines anupstream RF signal 116 from a device (e.g., the client device 15 (FIG.1), such as a set top box) with an upstream RF signal 117 from a device(e.g., the client device 13 (FIG. 1)) to provide an upstream RF signal118 to the source via the entry port 103. In some implementations, thesplitter/combiner 110 can equally split the downstream RF signal 113received at the common terminal (C) between the legs (1, 2). In otherimplementations, the splitter/combiner 110 can split the downstream RFsignal 113 into non-equal portions. For example, the splitter/combiner110 can be a directional coupler that provides a majority (e.g., >50%)of the downstream RF signal 113 to the second leg (2), which feeds thepassive path 112.

The active path 111 communicatively links bidirectional RF signals 113,114, 116, 118 between the entry port 103 and the active port 108. Theactive path 111 includes at least one active device (e.g., amplifiers135 and 137) powered by a power source (e.g., power 109 from the powerinput port 105 provided via the regulator 151). In some implementations,the active path 111 includes the first leg (1) of the splitter/combiner110 and a device 106 which includes: a switch 121, a buffer 123, asecond switch 125, and an amplifier circuit 127. As used herein, abuffer may also be referred to as an attenuator/isolator and may be usedto buffer, attenuate, and/or isolate signals.

In some implementations, the device 106 can include a first switch 121,buffer 123, and a second switch 125. The switches 121 and 125 provide aswitching element (also referred to as a switching circuit) thatbypasses the buffer 123 as described herein. The switches 121 and 125can be relays having a common terminal (C), a normally-closed (NC)terminal and a normally-open (NO) terminal. For example, as illustratedin FIG. 2, the switches 121 and 125 can be single-pole, dual-throw(SPDT) non-latching relays. However, it understood that other types ofrelays can be implemented (e.g., dual-poll, dual terminal relays). Insome implementations, the switches 121 and 125 can be mechanical relays.In other implementations, the switches 121 and 125 can be solid-staterelays. The common terminal (C) is electrically connected to thenormally-closed terminal (NC) when the switches 121 and 125 are notpowered. On the other hand, the common terminal (C) is electricallyconnected to the normally-open (NO) terminal when the switches 121 and125 are powered. For example, when energized with an operating voltageprovided from the power input port 105 via, e.g., a regulator 143, theswitches 121 and 125 are placed in a first state in which the commonterminal (C) connects to the normally-open terminal (NO). When theswitching element is not energized, the common terminal (C) connects tothe normally-closed terminal (NC). Thus, the common terminal (C) of eachof the switches 121 and 125 connects to the normally-closed terminals(NC) if the network interface device 10 loses power 109, if theregulator 151 fails, or if the fault detector 153 interrupts the power109 in response to a fault condition.

The buffer 123 can be electrically connected between the normally-openterminals of the switches 121 and 125 such that the buffer 123 isincluded in the active path 111 in the event that the switches 121 and125 are not energized. The buffer 123 can be configured to increase theisolation of the active path 111 from the passive path 112 byautomatically placing a resistive attenuator or absorptive filterbetween the active path 111 and the passive path 112. In embodiments,the buffer 123 attenuates upstream and/or downstream RF signals best atlevels greater than 10 dB.

The amplifier circuit 127 can include one or more active componentscapable of electrically controlling electron flow (i.e., current). Insome implementations, the amplifier circuit 127 can include a firstdiplexer 133, a downstream amplifier 135, upstream amplifier 137, and asecond diplexer 139. The diplexers 133 and 139 can be passive devicesthat separate RF signals received at a common terminal (S) into a highfrequency band and a low frequency band. The high frequency band signalis output from the high terminal (H) and the low frequency band signalsare output from the low terminal (L). In the reverse direction, thediplexers 133 and 139 multiplex signals received at the high terminal(H) and the low terminal (L) into a single signal, which is output fromthe common terminal (C). In some implementations, the diplexers 133 and139 filter RF signals such that frequencies greater than about 54 MHz(e.g., a CATV downstream frequency band) are passed bidirectionallybetween the common terminal (C) to the high terminal (H), andfrequencies less than about 42 MHz (e.g., a CATV upstream frequencyband) are passed bidirectionally between the common terminal (C) to thelow terminal (L).

The passive path 112 is a signal path through the network interfacedevice 10 that is entirely devoid of any active devices. The passivepath 112 communicatively links bidirectional RF signals (e.g., RFsignals 115 and 117) between the entry port 103 and the passive port107. The passive path 112 can include the second leg (2) of thesplitter/combiner 119, which can transmit bidirectional RF signals 113,115, 117, and 118 between the entry port 103 and the passive port 107.Additionally, in some implementations, the passive path 112 can includean un-powered passive device 143, made up of solely of non-activedevices, such as resistors, capacitors, inductors, transformers, and/ordiodes. For example, the passive device 143 can include one or morepassive filters or attenuators for conditioning RF signals 114 and 116.

During normal operation of the network interface device 10, the variouspowered devices (e.g., switches 121 and 125) or active components (e.g.,amplifiers 135 and 137) contained therein are powered via power 109received via the power input port 105. Accordingly, the switches 121 and125 communicate the RF signals 114 and 116 through the active path 111via the amplifier circuit 127, bypassing the buffer 123. In the event ofa condition that interrupts the power 109 and/or voltage V, the switches121 and 125 switch the active path 111 through the normally-openterminals (NO), which direct the RF signals 114 and 116 through thebuffer 123. As such, the RF signals 114 and 116 are substantiallyattenuated or terminated by the buffer 123 such that the downstream RFsignal 114 is not reflected back to the splitter/combiner 110 (or atleast such reflections are attenuated), and the upstream RF signal 116is not communicated to the splitter/combiner 110. Interference fromnoise and reflections from the RF signals 114 and 116 into the entryport 103 and the passive port 107 from the active path 111 during afault condition are, thereby, minimized. Accordingly, during power lossor a fault condition, the network interface device 10 minimizes oreliminates signal interference in the passive path 112 from the activepath 111 so that a device (e.g., a passive client device 13 (FIG. 1),such as a VOIP device) connected to the passive port 107 can continue tocommunicate via the entry port 103 with little or no effects ofinterference from the active path 111.

In FIG. 2B, a shunt buffer 140 may be connected to the switch 121. Theshunt buffer 140 may not be connected to the switch 125. When the shuntbuffer 140 is in use, the buffer 123 and/or the switch 125 may beomitted. All or a portion of the shunt buffer 140 may be or include anattenuator, a resistor, absorptive ferrite, an absorptive low-passfilter, high-pass or a band-pass filter, and/or a phase-cancellationcircuit. Examples may be seen in FIGS. 3A, 3B, 4-6, and 9B.

The shunt buffer 140 may include a first inductor 141, a resistor 142,and a first capacitor 143 in series. A second capacitor 144 may beconnected between the first inductor 141 and the resistor 142. Thesecond capacitor 144 may be grounded. A second inductor 145 may beconnected in parallel with the first capacitor 143. The first capacitor143 and the second inductor 145 may also be connected to ground. As willbe appreciated, the buffers 123, 140 are merely illustrative, and anyattenuator may be used. For example, in one embodiment, the buffer 123may be in a shunt configuration, and all of the internal circuitelements thereof may also be as effective in the shunt configuration.Additionally, the buffer 140 may be in a series configuration, and allof the internal circuit elements thereof may also be as effective in theseries configuration. Another embodiment of the series buffer 140 isshown in FIG. 9C.

FIG. 3A is a functional block diagram of a buffer 123 in accordance withsome implementations consistent with the present disclosure. The buffer123 can be a passive device including resistive elements that attenuateRF signals 114 and 116. In some implementations, the buffer 123 caninclude resistors 303, 305, and 307. The resistor 305 can be positionedin series with the RF signals 114 and 116. The resistor 303 can have afirst end connected to an upstream end of resistor 305 and a second endconnected to the circuit common or ground. The resistor 307 can beparallel to the resistor 303. For example, a first end of the resistor307 can be connected to a downstream end of resistor 305, and a secondend of the resistor 307 connected to the circuit common or ground. Insome implementations, resistors 303, 305, and 307 of the buffer 123attenuate the power of RF signal 116 by 10 dB and attenuate the power ofreflected RF signal 114 by 20 decibels (dB).

FIG. 3B is a functional block diagram of a resistive buffer 123 inaccordance some implementations consistent with the present disclosure.The buffer 123 can include resistors 303 and 305, which can be the sameor similar to those described above. The resistors 305 can be positionedin series. The resistor 303 can have a first end connected to anupstream end of resistor 305 and a second end connected to the circuitcommon or ground. In some implementations, resistors 303, 305 of thebuffer 123 attenuate the power of RF signal 116 by 10 dB and attenuatethe power of reflected RF signal 114 by 20 dB.

FIG. 4 is a functional block diagram of a matched resistive buffer 123in accordance with aspects of the present disclosure. The buffer 123 caninclude resistors 303, 305, and 307, which can be the same or similar tothose described above. Additionally, the buffer 123 can include reactivematching elements 403, 405, 407, and 409 to better match the impendenceof the signal path carrying the RF signals 114 and 116 (e.g., the activepath 111) than a similar circuit lacking such elements. The matchingelements 403 and 407 can be inductive elements having inductances in therange of about 3 nanohenries (nH) or less. The matching elements 405 and409 can be capacitive elements having capacitances in a range of about0.5 pF or less.

FIG. 5 is a functional block diagram of an absorptive low pass filterbuffer 123 in accordance with aspects of the present disclosure. Thebuffer 123 can be a passive device including an absorptive high-passfilter 503 that absorbs frequencies greater than a predetermined value.In some implementations, the high-pass filter 503 filters the entireCATV band. For example, the high-pass filter 503 can filter and/orabsorb frequencies less than or equal to about 1002 MHz.

FIG. 6 is a functional block diagram of an absorptive high pass filterbuffer 123 in accordance with aspects of the present disclosure. Thebuffer 123 can be a passive device including an absorptive low-passfilter 603 that absorbs frequencies less than predetermined value. Insome implementations, the low-pass filter 603 filters the entire CATVband. For example, the low-pass filter 603 can filter and absorbfrequencies greater than or equal to about 5 MHz.

FIGS. 7A and 7B are functional block diagrams of a multi-output networkinterface device 700 in accordance with aspects of the presentdisclosure. The network interface device 700 can include an entry port103, a power input port 105, a passive port 107, active ports 108A . . .108N, a splitter/combiner 110, a first switch 121, a buffer 123, asecond switch 125, and an amplifier circuit 127, which can be the sameor similar to those previously described herein. Additionally, thenetwork interface device 700 can include a one-in, multiple-outsplitter/combiner 703 electrically connected between the amplifiercircuit 127 and the active output 109. More specifically, thesplitter/combiner 703 can include a number (N) of outputs, one or moreof which can be electrically coupled to respective active ports 108A . .. 108N for communicating RF signals (e.g., RF signals 114 and 116) torespective client devices (e.g., client device 15 (FIG. 1)).Accordingly, the network interface device 700 can communicate with anumber (N) of subscriber equipment devices.

In FIG. 7B, the series buffer 140 may be connected to the switch 121.The series buffer 140 may not be connected to the switch 125. When theseries buffer 140 is in use, the buffer 123 and/or the switch 125 may beomitted. All or a portion of the series buffer 140 may be or include anattenuator, a resistor, absorptive ferrite, an absorptive low-passfilter, high pass filter, band-pass filter, and/or a phase-cancellationcircuit. In at least one embodiment, the series buffer 140 may beequivalent to the buffer 123, with the difference being that one is inseries between relays and the other is shunted after the relay 121 orbetween the relays.

FIG. 8 is a functional block diagram of an example of a multi-outputnetwork interface device 800 in accordance with aspects of the presentdisclosure. The network interface device 800 can include an entry port103, a power input port 105, a passive port 107, active ports 108A . . .108N, a splitter/combiner 110, active path 111, passive path 112, and asplitter/combiner 703, all of which can be the same or similar to thosepreviously described herein. Additionally, the network interface device800 can include a buffer 826 that provides a similar functionality tothe attenuation/isolation (e.g., device 106) previously describedherein. In some implementations, the buffer 826 can be an active, solidstate device that can selectively pass RF signals 114, 116 through theactive path 111 when the buffer 826 is in a first state (e.g., energizedor powered). And, the buffer 826 can isolate and/or absorb, attenuate,terminate, or isolate RF signals 114, 116 and any reflected signals whenthe buffer 826 is in a second state (e.g., de-energized or unpowered).For example, the second state can occur due to a loss of power or apower fault condition that de-energizes the buffer 826. In such state,the buffer 826 minimizes or eliminates signal interference in thepassive path 112 from the RF signals 114, 116 of the active path 111 sothat a device (e.g., a passive client device 13) connected to thepassive port 107 can continue to communicate via the entry port 103 withlittle or no interference from RF signals 114, 116 of the active path111.

FIG. 9A is a functional block diagram of an example of the buffer 826 inaccordance with aspects of the present disclosure. The buffer 826includes a signal path that conducts RF signals 114 and 116 betweennodes 905 and 907 via a diode 909, and an attenuator including atransistor 911. In some implementations, the buffer 826 can be asolid-state device that lacks any mechanical switches (e.g., switches121 and 125).

As described above, the buffer 826 can have two states: a first statethat exists when buffer 826 is energized by a voltage source V (e.g.,from power input port 105 and/or regulator 101), and a second state thatexists when the buffer 826 is de-energized (e.g., by a loss of power outto/from regulator 101 or power input port 105, or cutoff of power byfault detector 102). When the buffer 826 is energized in the firststate, the buffer 826 can bidirectionally communicate RF signals 114 and116, in a similar manner to the buffers previously described herein. Inthe second state, when the buffer 826 is de-energized, the buffer 826prevents bidirectional communication of the RF signals 114 and 116, andinstead, provides isolation and impedance matching to prevent signalreflections in a similar manner to the buffers previously describedherein.

The flow of RF signals 114, 116 through the buffer 826 is controlled bythe operating states of the diode 909 and the transistor 911, which aredetermined by whether the voltage source V is energized, as in the firststate, or de-energized, as in the second state. In the first state, thevoltage source V connected to the source (S) of the transistor 911biases it to prevent flow of current between its drain D and source S.For example, as illustrated in FIG. 9, the transistor 911 can be ann-channel field-effect transistor (e.g., an n-channel JFET or MOSFET)having its gate (G) tied to ground and its source tied to the voltagesource V. Thus, in the first state, the power source V reverse-biasesthe transistor 911 such that it is in an off-state, and current does notflow through the transistor 911 between its drain D and source S.Additionally, in the first state, the voltage source V connected to theinput of the diode 909 forward biases the diode 909, which provides alow-loss (e.g., about 0 dB loss) signal path for RF signals 114 and 116between the nodes 905 and 907 through the diode 909. As such, the RFsignals 114 and 116 do not flow through resistors 913, 917, 919 orcapacitors 921, 923 due to their high resistance in comparison to thepath via the diode 909. Accordingly, in the first state, the RF signals114, 116 flow through the buffer 826 solely between nodes 905 and 907via the diode 909.

In the second state, when the voltage source V is de-energized (e.g., Vis about zero volts), the transistor 911 is unbiased to permit currentflow through its resistive structure, and the diode 909 is notforward-biased and thus blocks current flow via its open or highimpedance structure. For example, where the transistor 911 is anN-channel JFET, above, the lack of voltage from the power source V(e.g., PWR 109, regulator 101 and/or fault detector 102) un-biases thetransistor 911 such that it switches to a resistive state that permitscurrent flow to ground voltage 927. Additionally, when notforward-biased, the diode 909 blocks the flow of RF signals 114 and 116between nodes 905 and 907. Accordingly, the RF signals 114, 116 areshunted through the resistors 917, 913, 919 and the transistor 911 toground 927, and not communicated between the nodes 905 and 907 via thediode 909. The resistors 935 and 941 and inductors, 933 and 939 form adirect-current voltage (VDS) bias path for the diode 909, wherein theresistors can be current limiting in the range of about 200 ohms orgreater, and the inductors can be RF chokes in the range of about 4.7microhenries (μH) or greater. As such, resistors 935 and 941 andinductors, 933 and 939 isolate the signal path between nodes 905 and 907from the voltage source V and the ground 927.

FIG. 9B is a functional block diagram of an example of a shunt buffer950 in accordance with aspects of the present disclosure. The shuntbuffer 950 may be similar to the buffer 826 in FIG. 9A. However, in theshunt buffer 950, the resistor 913 (and the line in which it ispositioned), the resistor 917, the resistor 919 (and the line in whichit is positioned), and/or the capacitor 923 (and the line in which it ispositioned) may be omitted. In addition, a circuit element 952 may beconnected to the capacitor 951 (e.g., positioned between the capacitor951 and ground). The circuit element 952 may be or include anattenuator, a resistor, an absorptive ferrite, an absorptive low-passfilter, an absorptive band-pass filter, an absorptive high-pass filter,a phase-cancellation circuit, or a combination thereof. Examples of thecircuit element 952 may be seen in FIGS. 3A, 3B, and 4-6.

FIG. 9C is a functional block diagram of an example of a series buffer960 with a simplified absorptive band-pass filter in accordance withaspects of the present disclosure. The series buffer 960 may be similarto the series buffer 140 shown in FIG. 2A. In a first (e.g., normal)condition, the pin diode 909 may be closed, and signals pass in and out.In the first (e.g., normal) condition, the transistor (e.g., FET) 911may be open, and the signal may be isolated from ground. In a second(e.g., error or power off) condition, the pin diode 909 may be open, andsignals may be blocked in and out. In the second (e.g., error or poweroff) condition, the transistor (e.g., FET) 911 may be closed, and thesignal may be absorbed in the absorptive band-pass filter. In apower-off condition, the transistor (e.g., FET) 911 may be or include asmall resistance, and signal may be absorbed in the absorptive band-passfilter.

In FIGS. 9B and 9C, the diode 909 and the transistor (e.g., FET) 911 mayform a single pole, double throw (SPDT) with the input as the common andthe output and ground as the two outputs.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims. The presentdisclosure is not to be limited in terms of the particular embodimentsdescribed in this application, which are intended as illustrations ofvarious aspects. Many modifications and variations can be made withoutdeparting from its spirit and scope, as will be apparent to thoseskilled in the art. Functionally equivalent apparatuses within the scopeof the disclosure, in addition to those enumerated herein will beapparent to those skilled in the art from the foregoing descriptions.Such modifications and variations are intended to fall within the scopeof the appended claims. The present disclosure is to be limited only bythe terms of the appended claims, along with the full scope ofequivalents to which such claims are entitled. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should be interpreted to mean “at least one”or “one or more”); the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention (e.g., “asystem having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc.). In those instances where a convention analogous to “atleast one of A, B, or C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one of A, B, or C” wouldinclude but not be limited to systems that have A alone, B alone, Calone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc.). It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” will be understood to include thepossibilities of “A” or “B” or “A and B.” In addition, where features oraspects of the disclosure are described in terms of Markush groups,those skilled in the art will recognize that the disclosure is alsothereby described in terms of any individual member or subgroup ofmembers of the Markush group.

What we claim is:
 1. A network interface device, comprising: an entryport configured to connect the network interface device to aradio-frequency (RF) signal source; a splitter/combiner configured tosplit a downstream RF signal received by the entry port from the RFsignal source into a first portion of the downstream RF signal and asecond portion of the downstream RF signal; a passive port configured toconnect the network interface device to a first client device; an activeport configured to connect the network interface device to a secondclient device; a passive RF signal path coupling the entry port to thepassive port; an active RF signal path coupling the entry port to theactive port; and an amplifier circuit configured to amplify the secondportion of the downstream RF signal in the active RF signal path;wherein the active port is configured to provide an upstream RF signalthrough the amplifier circuit to the entry port.
 2. The networkinterface device of claim 1, wherein the active RF signal path comprisesa decibel limiting device, wherein the decibel limiting device comprisesan active device, and wherein the passive RF signal path lacks anyactive devices.
 3. The network interface device of claim 1, wherein acommon terminal of the splitter/combiner is configured to receive thedownstream RF signal as an input from the RF signal source via the entryport.
 4. The network interface device of claim 1, further comprising: apower supply; wherein the active RF signal path comprises a decibellimiting device comprising a first relay, a second relay, and a buffer,and wherein the first relay and the second relay, when actuated into afirst state by the power supply, are configured to direct the upstreamRF signal and the second portion of the downstream RF signal to bypassthe buffer.
 5. The network interface device of claim 4, wherein thefirst relay and the second relay, when actuated into a second state bythe power supply, are configured to direct the upstream RF signal andthe second portion of the downstream RF signal to the buffer.
 6. Thenetwork interface device of claim 4, wherein a first leg of thesplitter/combiner is configured to output the first portion of thedownstream RF signal to the passive port.
 7. The network interfacedevice of claim 6, wherein a second leg of the splitter/combiner isconfigured to output the second portion of the downstream RF signal to acommon terminal of the first relay.
 8. The network interface device ofclaim 4, wherein: a normally-open terminal of the first relay isconfigured to provide the second portion of the downstream RF signal tothe buffer; and a normally-open terminal of the second relay isconfigured to provide the upstream RF signal to the buffer.
 9. Thenetwork interface device of claim 4, wherein: a normally-closed terminalof the first relay is configured to provide the second portion of thedownstream RF signal to a normally-closed terminal of the second relay;and a normally-closed terminal of the second relay is configured toprovide the upstream RF signal to a normally-closed terminal of thefirst relay.
 10. The network interface device of claim 4, wherein acommon terminal of the second relay is configured to output the secondportion of the downstream RF signal to the active port through theamplifier circuit.
 11. A network interface device, comprising: an entryport configured to receive a downstream radio-frequency (RF) signal froma signal source; a first port configured to receive a first portion ofthe downstream RF signal from the entry port via a passive path andconfigured to transmit a first upstream RF signal to the entry port viathe passive path; a second port configured to receive a second portionof the downstream RF signal from the entry port via an active path andconfigured to transmit a second upstream RF signal to the entry port viathe active path; and a decibel limiting device in the active path havinga first state and a second state, the decibel limiting device beingconfigured to: in the first state, pass the second portion of thedownstream RF signal and the second upstream RF signal via the activepath, and in the second state, absorb, attenuate, terminate, or isolatethe second portion of the downstream RF signal, the second upstream RFsignal, or both by at least 10 decibels.
 12. The network interfacedevice of claim 11, further comprising a splitter/combiner configuredto: split the downstream RF signal into the first portion in the passivepath and the second portion in the active path; and combine the firstupstream RF signal from the passive path with the second upstream RFsignal from the active path.
 13. The network interface device of claim11, further comprising an amplifier circuit in the active pathconfigured to amplify the second portion of the downstream RF signal.14. The network interface device of claim 13, wherein the amplifiercircuit is further configured to amplify the second upstream RF signal.15. The network interface device of claim 13, wherein, in the secondstate, the decibel limiting device is configured to absorb, attenuate,terminate, or isolate RF signals reflected by the amplifier circuit. 16.The network interface device of claim 11, wherein: the decibel limitingdevice is configured to be in the first state during powered operationof the network interface device; and the decibel limiting device isconfigured to be in the second state during unpowered operation orfaulted operation of the network interface device.
 17. The networkinterface device of claim 11, wherein the passive path lacks any activedevices.
 18. The network interface device of claim 11, wherein: thedecibel limiting device comprises a first relay, a buffer, and a secondrelay; in the first state, the first and second relays are configured todirect the second portion of the downstream RF signal and the secondupstream RF signal to bypass the buffer; in the second state, the firstand second relays are configured to direct the second portion of thedownstream RF signal and the second upstream RF signal to the buffer;and the buffer is configured to absorb, attenuate, terminate, or isolatethe second portion of the downstream RF signal and the second upstreamRF signal.
 19. The network interface device of claim 11, wherein thebuffer comprises: a diode configured to: in the first state, communicatethe second portion of the downstream RF signal and the second upstreamRF signal between the entry port and the second port, and in the secondstate, block communication of the second portion of the downstream RFsignal and the second upstream RF signal between the entry port and thesecond port; and a circuit configured to, in the second state, absorb,attenuate, terminate, or isolate the second portion of the downstream RFsignal and the second upstream RF signal.
 20. A network interfacedevice, comprising: a passive path between an entry port and a firstport; an active path between the entry port and a second port; a bufferin the active path configured to absorb, attenuate, terminate, orisolate radio-frequency (RF) signals; and a switching element in theactive path configured to: cause the RF signals to bypass the bufferwhen the network interface is in a first state that exists duringpowered operation of the network interface device, and direct the RFsignals to the buffer when the network interface device is in a secondstate that exists during non-powered operation or faulted operation ofthe network interface device.
 21. The network interface device of claim20, wherein: the passive path lacks any active devices; and the activepath includes at least one active device.
 22. The network interfacedevice of claim 21, wherein the at least one active device comprises anamplifier circuit configured to amplify the RF signals in the activepath.
 23. The network interface device of claim 22, wherein the RFsignals in the active path comprise a downstream RF signal and anupstream RF signal.
 24. The network interface device of claim 20,further comprising a splitter/combiner configured to: split a downstreamRF signal received from the entry port between the active path and thepassive path; and combine a first upstream RF signal received from thepassive path with a second upstream RF signal received from the activepath.
 25. The network interface device of claim 20, wherein theswitching element comprises a first relay and a second relay, andwherein: in the first state, the first relay and the second relay areconfigured to cause a downstream RF signal and an upstream RF signal tobypass the buffer; in the second state, the first relay and the secondrelay are configured to direct the downstream RF signal and the upstreamRF signal to the buffer; and the buffer is configured to absorb,attenuate, terminate, or isolate the downstream RF signal and theupstream RF signal.
 26. The network interface device of claim 20,wherein the buffer comprises a shunt buffer, wherein the switchingelement comprises a single relay, and wherein: in the first state, thesingle relay is configured to cause a downstream RF signal and anupstream RF signal to bypass the buffer; in the second state, the singlerelay is configured to direct the downstream RF signal and the upstreamRF signal to the buffer; and the buffer is configured to absorb,attenuate, terminate, or isolate the downstream RF signal and theupstream RF signal.
 27. A network interface device having a first portconfigured to allow a downstream radio-frequency (RF) signal receivedfrom a signal source to be communicated through the network interfacedevice, and a second port configured to allow an upstream RF signal tobe communicated to the first port, the network interface devicecomprising: a decibel limiting device configured to switch between afirst state, where the downstream RF signal and the upstream RF signalare permitted to be communicated between the first and second ports, anda second state, where the downstream RF signal and the upstream RFsignal are restricted from communicating between the first and secondports by a predetermined decibel limit.
 28. The network interface deviceof claim 27, wherein the first port comprises an entry port configuredto allow the downstream RF signal received from the signal source to becommunicated to an active path in the network interface device, whereinthe second port is configured to allow a first upstream RF signal to becommunicated to the first port, and wherein the network interface portfurther comprises a second port configured to allow a second upstream RFsignal to be communicated to the entry port.
 29. The network interfacedevice of claim 28, wherein the second upstream RF signal iscommunicated through a passive path that lacks any active devices. 30.The network interface device of claim 27, wherein the predetermineddecibel limit comprises at least 10 decibels.
 31. A network interfacedevice having a first port configured to allow a downstream signalreceived from a signal source to be communicated through the networkinterface device, and a second port configured to allow an upstreamsignal to be communicated to the first port, the network interfacedevice comprising: a decibel limiting device configured to switchbetween a first state, where the downstream signal and the upstreamsignal are permitted to be communicated between the first and secondports, and a second state, where the downstream signal and the upstreamsignal are restricted from communicating between the first and secondports by a predetermined decibel limit.
 32. The network interface deviceof claim 31, wherein the predetermined decibel limit comprises at least10 decibels.
 33. The network interface device of claim 31, wherein thedownstream signal comprises a downstream radio-frequency (RF) signal,and the upstream signal comprises an upstream RF signal.
 34. The networkinterface device of claim 31, wherein the decibel limiting devicecomprises: a switch configured to actuate between the first state andthe second state; and a buffer, wherein the switch causes the downstreamsignal and the upstream signal to bypass the buffer when the switch isin the first state, and wherein the switch directs the downstream signaland the upstream signal to the buffer when the switch is in the secondstate to cause the buffer to restrict the downstream signal and theupstream signal from communicating between the first and second ports bythe predetermined decibel limit.